I had a hippo in a 90 gallon that didn't look that bad, but maybe earlier stages of that. It looked like it was driving itself into the crevices of rocks and really getting scraped up. I fed it well, soaked foods in Vita-chem, zoe, and zoe-con as well as garlic. Tried everything.
I recently set up a 265 gallon tank and moving it over there improved the condition dramatically, although I feel there are areas that are scarred.
Curious to know how much swimming room is available in your tank and how big the fish is. I feel that mine outgrew the tank and I left very little room with the additions of live rock taking up a great deal of the space.
I hope your fish improves.
A great resource is Kelly Jedlicki and you can find her at the Marine Depot forums in a section titled "Disease, Health, and Wellness" http://forum.marinedepot.com/Forum10-1.aspx